1. Field of the Invention
The invention relates to a wheel assembly with an in-wheel motor, which transmits rotational output of the motor to a wheel via a counter gear.
2. Description of the Related Art
Japanese Patent Application Publication No. JP-A-2005-335623, for example, describes a related wheel assembly with an in-wheel motor, which reduces (i.e., slows or decelerates) rotational output of a motor and then transmits it to a wheel. In this wheel assembly with an in-wheel motor, an oil pump is driven by a shaft that rotates at a slowed rate.
However, with the invention described in Japanese Patent Application Publication No. JP-A-2005-335623, a planetary gear set, which serves as the reduction mechanism, is arranged concentric and in series with the motor. Thus, with this structure it is easy to supply oil from the oil pump to the planetary gear set, but not easy to supply oil from the oil pump to the motor.
In contrast, when the oil pump is operated using the rotational output of the motor, the oil pump can be arranged close to the motor which makes it easier to supply oil from the oil pump to the motor. In this case, however, the oil pump is driven by a shaft that does not rotate at a slowed rate, which is disadvantageous from the viewpoint of durability of the oil pump.